Riak is NOT an SQL-like system -> yep, i know that and its query limitations,
however, i thought that doing a pagination would be a piece of cake :P
thanks for the reply : )
Rohman
Antonio Rohman Fernandez
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On Mar 10, 2011, at 9:37 PM, Sean Cribbs wrote:
>
> On Mar 10, 2011, at 8:26 AM, Antonio Rohman Fernandez wrote:
>
>> Dear Sean,
>> thank you for your quick reply.
>>
>> "Your reduce function can (almost) never assume that it is operating on the
>> entire result set." -> wow! that totally kills my implementation... i wanted
>> to use the Reduce phase to cut the array as a Limit + Pagination ( like
>> LIMIT 10 PAGE 2 in SQL )... but if i don't have the full result set is
>> impossible and useless. I will have to get all the rows and then process it
>> outside Riak for that.
>>
>
> Note I said "(almost)". In the case where the reduce phase is preceded by
> another reduce phase, you can generally assume that it will only be executed
> once. So, pagination is hard to do but not impossible - do a sorting phase
> before your limit/slice.
>
>> "you must structure your reduce function such that it can receive as inputs
>> anything that it outputs" -> what do you mean with that? can i merge Reduce
>> phases? any example?
>>
>
> What that means is any data you return might again become inputs to the same
> function as I described. The properties we say are needed for reduce
> functions are "commutative, associative, and idempotent". Commutative - it
> can be applied in any order and produce the same result. Associative - any
> grouping of the same inputs will produce the same result. Idempotent - given
> the same inputs, you will get the same result every time (i.e. it has no
> side-effects).
>
>> i'm building a php MVC framework in top of Riak, and i would like to clone
>> from my SQL implementation as much functionality as i can, so people can
>> easily use Riak as if they were using MySQL/PostgreSQL/etc without noticing.
>> thanks.
>
> I can understand the desire to provide similar functionality, but Riak is NOT
> an SQL-like system. Having tried some similar things in Ruby, I believe it's
> ok to provide your users a nice interface, but don't delude them about having
> the same querying capabilities -- it's just NOT the same. It's better to
> craft the features in a way that exposes tradeoffs to them rather than hiding
> them.
>
> Sean Cribbs <[email protected]>
> Developer Advocate
> Basho Technologies, Inc.
> http://basho.com/
>
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